[Objective] In order to understand the prevalence of Brucellosis in dairy animals in Yanggu County,Shandong Province. [Method] serological surveillance and investigation of 9 198 non-immune serum samples collected from 718 large-scale cow and dairy goat farms and free-range households in the county from 2020 to 2023 were carried out for four consecutive years.Brucellosis was detected by the combination of primary screening of rose bengal plate agglutination test and confirmed by tube agglutination test.SPSS 22 was used to analyze the relevant monitoring indicators,and the positive field group was traced and the epidemic situation was disposed. [Result] The results showed that the positive rate of cow and dairy goat Brucellosis in Yanggu County from 2020 to 2023 was 1.95%,and the individual positive rate was 0.60%.From 2020 to 2023,the positive rates of field groups were 2.04%,3.01%,1.91% and 1.08%（P<0.05）,and the positive rates of individuals were 0.46%,1.01%,0.91% and 0.35%,respectively.The positive rates of large-scale farms and free-range households were 1.67% and 2.09%,respectively（P<0.05）.The individual positive rates of large-scale farms and free-range farmers were 0.53% and 0.65%,respectively. [Conclusion] The results showed that the prevalence of brucellosis in cattle and sheep in Yanggu County was low,but there was still a risk of spreading.It is necessary to strengthen continuous monitoring and implement various prevention and control measures.